Page 4 - NutrientsReadMe

In general, errors in any nutrient dataset can arise from handling problems (including
mislabelling of samples, problems in filtering, and problems arising from not freezing rapidly
enough and/or subsequent thaw/freeze cycles), as well as analytical problems in the
laboratory, and it is important to consider the effects of these errors.
A standard quality-control practice is to
examine correlations between the different
nutrients in property/property plots. Nutrient
concentrations in the ocean generally co-vary
in relatively fixed ratios with each other (so-
-
called “Redfield” ratios, for which NO3
3-
:Si:PO4 are in proportions of 16:15:1) because
their concentrations are controlled by
phytoplankton uptake and remineralization
processes, and phytoplankton contain
nitrogen, silicon, and phosphorus in (more or

1A Nutrient auto-analyzer. Vials are placed in racks in less) these ratios. Offsets from curves with
the loading mechanism at left, and then samples are these slopes that pass through the origin are
automatically pumped into the thin. tubes moving often used to infer the effects of denitrification,
towards the analyzer itself at right.
a microbial process that converts organic
nitrogen into nitrogen gas. This is probably not an important part of the Strait of Georgia
ocean ecosystem, but may be important in the open ocean regions from which the Strait of
Georgia waters are sourced.

Nutrient ratios for CitSci data, by year. Upper row are nitrate/phosphate correlations, lower
row are nitrate/silicic acid correlations. The dashed lines indicate Redfield ratios.